1. Field of the Invention
The present invention relates to an electronic apparatus including a heat generating element, e.g., a notebook PC (personal computer) including a heat generating element such as a CPU (central processing unit). In particular, the present invention relates to a heat dissipation structure for dissipating heat from the heat generating element.
2. Description of Related Art
For example, in the case of a notebook PC, the amount of heat generated from a heat generating element such as a CPU increases as the performance of the notebook PC is improved. Therefore, it is likely that the configuration of a conventional heat dissipation device cannot dissipate heat sufficiently. Thus, a high-performance heat dissipation structure has been demanded. For example, when the heat dissipation structure uses an air flow produced by a cooling fan, the shape and arrangement of a heat dissipation fin, the interrelationship between the heat dissipation fin and a cooling fan, or the like have to be optimized.
Moreover, in the case of the electronic apparatus for which compactness is critical such as the notebook PC, the arrangement of the cooling fan and the heat dissipation fin is limited strictly. Under these circumstances, e.g., JP 2007-324339 A discloses a notebook PC having a heat dissipation structure, as shown in FIG. 19.
In this heat dissipation structure, a heat dissipation chamber 33 is formed by a partition 32 in a case 31, and a heat dissipation member 34 and a cooling fan 35 are located in the heat dissipation chamber 33. Although not shown in FIG. 19, heat is transferred from a heat generating component located inside the case 31 to the heat dissipation member 34 through the partition 32 via a heat-transfer member. The case 31 has a shape such that the lower portions of the heat dissipation chamber 33 and its adjacent area are open. The lower portion of the adjacent area to the heat dissipation chamber 33 is dosed off with a lower partition 36, thereby ensuring liquid tightness for components housed in the area of the case 31 other than the heat dissipation chamber 33.
The bottom including the lower portions of the heat dissipation chamber 33 and the lower partition 36 is dosed off with a cover 37. There is a gap S between the cover 37 and the lower partition 36. An outlet 38 communicating with the heat dissipation chamber 33 is provided in the side of the case 31, and inlets 39 are provided in the cover 37. A leg 40 is used to form a space between the bottom of the case 31 and a supporting surface F. Therefore, the heat dissipation chamber 33 communicates with outside air through the bottom of the case 31 via the inlets 39 and the gap S. By driving the cooling fan 35, the outside air is drawn through the inlets 39, blown toward the heat dissipation member 34, and exhausted from the outlet 38.
The heat dissipation structure disclosed in JP 2007-324339 A is intended to be compact with the effective use of a limited space in the case 31. However, it is difficult to make the heat dissipation structure sufficiently compact. This is because the lower partition 36 is required inside the bottom wall of the case 31 to form an intake path for the outside air, since the air is drawn through the bottom of the case 31.
Moreover, it is inevitable that the rigidity will be reduced in the area of the heat dissipation chamber 33 of the case 31. This is because, in order to form the heat dissipation chamber 33, the case 31 has to have a shape such that the lower portions of the heat dissipation chamber 33 and its adjacent area are open, and the bottom of the case 31 is dosed off with the cover 37.
On the other hand, another configuration can be considered, in which an inlet or outlet is provided while maintaining the bottom wall of a case, and a heat dissipation chamber is formed liquid tightly in the case using an internal partition. In this case, however, an air channel is needed to communicate the heat dissipation chamber with the inlet or outlet, and the air channel should be liquid tight to the inside of the case. Moreover, a decrease in the rigidity of the case caused by providing the inlet or outlet in the side wall of the case may be a problem.